Dependence of Brillouin Frequency Shift in Optical Fibers on Draw-Induced Residual Elastic and Inelastic Strains

The dependence of Brillouin frequency shift (BFS) in optical fibers on the residual elastic and inelastic strains induced by different draw tensions during fiber fabrication is investigated experimentally and theoretically. The BFS is linearly proportional to the draw tension with a measured coefficient of -42.0 MHz/100 g, which agrees with the theoretical value of -41.96 MHz/100 g. Theoretical analysis further shows that the elastic strain in fiber core influences predominantly the BFS due to the second-order nonlinearity of Young's modulus while the effect of the inelastic strain in fiber cladding is less than 1.0%.